HCl electrolysis frame with a graphite plate arranged therein

ABSTRACT

An HCl electrolysis frame with a graphite plate arranged therein, comprising expansion joints and optionally elastic seals arranged between the electrolysis frame and graphite plate, the connection between the electrolysis frame and the graphite plate being not rigid, and releasable connecting elements serving to hold the graphite plates.

United States Patent [191 Born et al.

[ HCl ELECTROLYSIS FRAME WITH A GRAPHITE PLATE ARRANGED THEREIN [75] Inventors: Hans Born; Karl-Josef Schwickart,

. both of Siershahn; Edmund Urban,

Boden; Wolf-Dieter Volkmann, Siershahn; Giinter Mohrs, Cologne, all of Germany [73] Assignees: Bayer Aktiengesellschaft,

Leverkusen; Gewerkschaft Keramchemie, Siershahn, both of Germany [22] Filed: Apr. 4, 1974 [21] Appl. No.: 457,737

[30] Foreign Application Priority Data Apr. 6, 1973 Germany 2317359 June 1, 1973 Germany 2327883 [52] US. Cl. 204/286; 204/128; 204/268; 204/294 [51] Int. Cl. C25B 11/12; C25B 11/12;

C25B 1/26; COIB 7/02 Primary ExaminerF. C. Edmundson Attorney, Agent, or FirmBurgess, Dinklage & Sprung [57] ABSTRACT An HCl electrolysis frame with a graphite plate arranged therein, comprising expansion joints and optionally elastic seals arranged between the electrolysis frame and graphite plate, the connection between the electrolysis frame and the graphite plate being not rigid, and releasable connecting elements serving to hold the graphite plates.

1 Claim, 6 Drawing Figures US. Patent 'Oct.28, 1975 Sheet10f3 3,915,836

FIG. lb

US. Patent Oct. 28, 1975 Sheet 3 of3 3,915,836

FIG. 4 FIG. 5

HCl ELECTROLYSIS FRAME WITH A GRAPHITE PLATE ARRANGED THEREIN The invention relates to an electrolysis plate consisting of an outer, non-conducting frame of asbestosstrengthened cresol resin and of an electrically conducting graphite plate which is arranged therein.

Such plates are usually arranged in blocks of 30 plates thus forming a unit for the electrolysis of hydrochloric acid. A direct current is conducted through the graphite plates splitting the hydrochloric acid into chlorine and hydrogen. The frames consisting of asbestosstrengthened cresol or phenolic resin insulate the graphite plates both outwardly and against each other. The hydrochloric acid is conducted through the frames by passing it in at the bottom and out at the top. In addition the gases forming during electrolysis (H and C1 are led off through specially arranged channels.

Hitherto, electrolyzer plates were so constructed that the graphite plate and the outer frame were seperately made of asbestos-strengthened cresol resin. After completion of the mechanical work on the frame, the graphite plate was inserted and connected to the frame using a chemically stable cold curing cementing composition.

Such plates have now been in use for a number of years. It has been found that after an operating period of 6 to 12 months the outer frames first crack at the gas channels. Cracks subsequently appear at various points over the entire cross section of the frame. As a result of these cracks the individual elements become unusable.

It is the object of the present invention to prevent cracks arising in these elements.

By means of detailed investigations it was determined that the asbestos-strengthened cresol resin shows abnormally pronounced shrinkage under the present operating conditions. This shrinkage was generally not detected in the case of asbestos-strengthened cresol and phenolic resin.

The object of the invention is attained by connecting the graphite plate and the frame in a new construction in such a way that no or only very slight tension is caused by strain-induced shrinkage.

The present invention relates to an HCl electrolysis frame with a graphite plate arranged therein, comprising expansion joints and optionally elastic seals arranged between the electrolysis frame and graphite plate, the connection between the electrolysis frame and the graphite plate being not rigid, and releasable connecting elements serving to hold the graphite plates.

Because the graphite plate is no longer rigidly connected to the outer frame a certain amount of movement, which is caused by shrinkage, is allowed for between the frame and the plate. This construction prevents thermal stress building up between the frame and graphite plate during operation of the apparatus.

As connecting pieces there may be used, for example, screw couplings, fastening members fixed by means of screws or cement, safety rods or cementing parts.

In the following different embodiments are described with reference to FIGS. 1 to 5.

FIG. la is a top view of an electrolysis unit.

FIGS. lb, 2, 3, 4 and 5 depict side views of the graphite plate with frame.

The numbers represent as follows:

I, 5, 9, l3, 17 electrolysis frame 2, 6, IO, 14, 18 graphite plate 3, 7, ll, l5, l9 =electrical seal 4, 8, l2, 16 releasable connecting elements 20 lined chamber 21 lined chamber 22 cementing part 23 cementing part 24 cementing part 25 circumferential groove One embodiment of the invention is shown in FIG. 2. When in operation the graphite plate 6 arranged within the electrolysis frame 5 rests on the lower part of the frame so that the weight of the graphite plate does not put a strain on the seal 4 fitted in the gap and composed of an elastic and stable material, for example polytetrafluoroethylene, chlorosulphonated polyethylene, polypropylene, asbestos cord, carbon fluoride rubber or the like. The upper gap allows movement of the frame upon shrinkage or thermal expansion. Upon shrinkage of the frame the gap becomes smaller and the elastic seal is compressed. The width of the gap is so calculated that full compensation is provided for the anticipated change in size. The arrangement of the graphite plate on the side faces corresponds to the example according to FIG. 2, upper part.

The electrolysis frame and the graphite plate are connected with one another by means of a 3 to 5 mm thick safety strip 8 of a stable material, e.g. normal or postchlorinated polyvinyl chloride or polypropylene.

This safety element 8 is inserted during assembly into the groove provided in the graphite plate 6 and electrolysis frame 5.

In the embodiment according to FIG. 3 the electrolysis frame 9 is sealed by an elastic O-ring 11 of a stable material. On assembly the O-ring is inserted into the groove provided therefor in the graphite plate 10 which is then placed in the electrolysis frame 9. The graphite plate 10 is fixed in said elelctrolysis frame by using a holding plate 12 composed of asbestos-strengthened cresol resin or glass fibre-strengthened plastic which is screwed or cemented onto the electrolysis plate from outside.

In the embodiment according to FIG. 4 the graphite plate 14 is directly connected with the electrolysis frame 13 by screws of stable material, such as postchlorinated polyvinyl chloride. An elastic flat seal 15 is placed between the graphite plate 14 and the electrolysis frame 13 to make a seal between the electrolysis frame 13 and the graphite plate 14. Movement between the electrolysis frame and the graphite plate is rendered possible by making the diameter of the bores for the screws 16 somewhat larger than the screw shaft. Since the screws 16 consist of a flexible plastic they can bend towards the graphite plate upon displacement of the electrolysis frame without breaking. The screw holes are sealed from the outside with a stable cement.

FIG. 5 shows another embodiment of the HCl electrolysis frame with a graphite plate arranged therein and elastic seals between the graphite plate and the electrolysis frame as well as releasable connecting ele ments between the electrolysis frame and the graphite plate. The cementing parts 22, 23 and 24, which are arranged on the graphite plate 18 or the electrolysis frame 17, prevent the graphite plate 18 from falling out of the electrolysis frame 17. The cementing parts are separated off from the graphite plate or electrolysis frame and from the elastic seals 19 by means of chambers 20, 21 provided with linings 21, however, can be removed again after application of the cementing parts.

The cementing parts 22, 23 and 24 on the graphite plate 18 and electrolysis frame 17 may consist of phenol formaldehyde resin or cresol formaldehyde resin.

Polyvinyl chloride, polyethylene or polypropylene may be used for the linings 20 and 21.

After hardening of the cementing parts the circumferential polyvinyl chloride, polyethylene or polypropylene strips 21 are removed so that there is a gap between the graphite plate and the electrolysis frame having the width of the strip which has been removed. Movement of the electrolysis frame towards the graphite plate is hence ensured.

To lessen the strain on the lower seal the graphite plate 18 supports itself during operation on the electrolysis frame 17, whilst there is clearance between the graphite plate and the electrolysis frame with respect to the two sides facing each other.

The graphite plate is likewise arrested at the upper side by the described cementing parts; however a connection is formed here between the cementing parts 23 and 24 and the graphite plate. The presence of an elastic seal between the electrolysis frame and graphite plate can be advantageous but is not obligatory; a releasable connecting element, for example in the form of a cementing part arranged on the electrolysis frame or on the graphite plate can seal off the expansion joint. Using this variant it must be ensured that the cementing part when arranged on the electrolysis frame does not form a rigid but a sliding connection with the graphite plate (in the case of a cementing part arranged on the graphite plate the connection with the electrolysis frame should accordingly not be rigid). A sliding connection between the cementing part and the graphite plate or electrolysis frame can be effected by providing those places of the graphite plate or electrolysis frame which come into contact with the cement with a thin protection coating.

The invention enables the graphite plate to be easily dismantled. Using a cutting device, which is guided in a groove 25 running around the electrolysis frame, the cementing parts can be cut off so that the graphite plate can easily be removed from the electrolysis frame.

By means of the device according to the invention cracks can be prevented, hence prolonging the life of the electrolyzer and rendering the process more economical.

We claim:

1. In an HCl-electrolysis plate and frame assembly comprising a frame, a graphite plate in said frame, re leasable connecting elements holding said plate in said frame, and non-rigid connectors between said plate and frame permitting expansion of the plate and relative movement between the plate and frame, the improvement comprising cementing parts on the graphite plate or on the electrolysis frame which are separated from the non-rigid connectors and the electrolysis frame or the graphite plate by chambers partly provided with linings or are separated from the electrolysis frame or the graphite plate by a thin protective coating and said frame is provided with a groove to guide a device for cutting off said cementing parts when it is desired to remove the plate from the frame. 

1. IN AN HCL-ELECTROLYSIS PLATE AND FRAME ASSEMBLY COMPRISING A FRAME, A GRAPHITE PLATE IN SAID FRAME, RELEASABLE CONNECTING ELEMENTS HOLDING SAID PLATE IN SAID FRAME, AND NON-RIGID CONNECTORS BETWEEN SAID PLATE AND FRAME PERMITTING EXPLANSION OF THE PLATE RELATIVE MOVEMENT BETWEEN THE PLATE AND FRAME, THE IMPROVEMENT COMPRISING CEMENTING PARTS ON THE GRAPHIC PLATE OR ON THE ELECTROLYSIS FRAME WHICH ARE SEPARATED FROM THE NON-RIGID CONNECTORS AND THE ELECTROLYSIS FRAME OR THE GRAPHITE PLATE BY CHAMBERS PARTLY PROVIDED WITH LININGS OR ARE SEPARATED FROM THE ELECTROLYSIS FRAME OR THE GRAPHITE PLATE BY A THIN PROTECTIVE COATING AND SAID FRAME IS PROVIDED WITH A GROOVE TO GUIDE A DEVICE FOR CUTTING OFF SAID CEMENTING PARTS WHEN IT IS DESIRED TO REMOVE THE PLATE FROM THE FRAME. 